Response to adrenocorticotropic hormone or corticotrophin-releasing hormone and vasopressin in lactating cows fed an immunomodulatory supplement under thermoneutral or acute heat stress conditions

Adrenal responsiveness was tested in nonpregnant, lactating Holstein dairy cows fed diets supplemented with OmniGen-AF (OG; Phibro Animal Health Corp., Teaneck, NJ), an immune modulator, and in nonsupplemented control (CON) cows following bolus infusions of a combination of corticotropin-releasing hormone (CRH; 0.3 µg/kg of BW) and arginine vasopressin (VP; 1.0 µg/kg of BW) or ACTH (0.1 IU/kg of BW) in 2 environments: thermoneutral [TN; temperature-humidity index (THI) <60] for 24 h/d and heat stress (HS; THI >68 for 17 h/d). Cows (506) were initially fed OG (n = 254) or CON (n = 252) diets for 44 d before selection of a subgroup of cows (n = 12; 6 OG, 6 CON) for the study. The 2 subgroups were balanced for parity, milk yield, and days in milk. All cows were transported to and housed in 2 environmentally controlled rooms at the University of Arizona Agricultural Research Complex (Tucson). Cows were given 3 d to acclimate to the rooms and then underwent 12 d of TN conditions and then 8 d of HS conditions for a total of 24 d on experiment. Cows were infused with CRH-VP on d 9 of TN and on d 1 of HS and with ACTH on d 10 of TN and on d 2 of HS. Hormone infusions took place at 1000 h (0 h) on each infusion day. Blood samples, taken in 30-min intervals, were first collected at 0800 h (-2 h) and were drawn until 1800 h (8 h). Before infusion, serum progesterone was elevated in OG cows compared with CON cows. Infusion of releasing factors (CRH-VP or ACTH) caused increases in serum cortisol and progesterone, but cortisol release was greater in CON cows than in OG cows during HS, whereas progesterone did not differ between the 2 treatments. Serum ACTH increased following infusion of releasing factors, but this increase was greater following CRH-VP infusion than ACTH infusion. Serum bovine corticosteroid-binding globulin also increased following infusion of releasing factors in both treatment groups, but this increase was greater during HS in cows fed OG. The free cortisol index (FCI) increased following CRH-VP and ACTH and was higher in HS than in TN for both OG and CON cows. However, the FCI response was blunted in OG cows compared with CON cows during HS. Heat stress enhanced the adrenal response to releasing factors. Additionally, the adrenal cortisol and FCI response to releasing factors was reduced during acute heat stress in cows fed OG. Collectively, these data suggest that OG supplementation reduced the adrenal responsiveness to factors regulating cortisol secretion during acute HS.

Changes in primary care provider utilization by phase of care for women diagnosed with breast cancer: a CanIMPACT longitudinal cohort study

BACKGROUND

Primary care providers (PCPs) have always played an important role in cancer diagnosis. There is increasing awareness of the importance of their role during treatment and survivorship. We examined changes in PCP utilization from pre-diagnosis to survival for women diagnosed with breast cancer, factors associated with being a high user of primary care, and variation across four Canadian provinces.

METHODS

The cohorts included women 18+ years of age diagnosed with stage I-III invasive breast cancer in years 2007-2012 in British Columbia (BC), Manitoba (MB), Ontario (ON), and Nova Scotia (NS) who had surgery plus adjuvant chemotherapy and were alive 30+ months after diagnosis (N = 19,589). We compared the rate of PCP visits in each province across phases of care (pre-diagnosis, diagnosis, treatment, and survival years 1 to 4).

RESULTS

PCP use was greatest during treatment and decreased with each successive survival year in all provinces. The unadjusted difference in PCP use between treatment and pre-diagnosis was most pronounced in BC where PCP use was six times higher during treatment than pre-diagnosis. Factors associated with being a high user of primary care during treatment included comorbidity and being a high user of care pre-diagnosis in all provinces. These factors were also associated with being a higher user of care during diagnosis and survival.

CONCLUSIONS

Contrary to the traditional view that PCPs focus primarily on cancer prevention and early detection, we found that PCPs are involved in the care of women diagnosed with breast cancer across all phases of care.

Cross-Canada differences in early-stage breast cancer treatment and acute-care use

Background

Chemotherapy has improved outcomes in early-stage breast cancer, but treatment practices vary, and use of acute care is common. We conducted a pan-Canadian study to describe treatment differences and the incidence of emergency department visits (edvs), edvs leading to hospitalization (edvhs), and direct hospitalizations (hs) during adjuvant chemotherapy.

Methods

The cohort consisted of women diagnosed with early-stage breast cancer (stages i-iii) during 2007-2012 in British Columbia, Manitoba, Ontario, or Nova Scotia who underwent curative surgery. Parallel provincial analyses were undertaken using linked clinical, registry, and administrative databases. The incidences of edvs, edvhs, and hs in the 6 months after treatment initiation were examined for patients treated with adjuvant chemotherapy.

Results

The cohort consisted of 50,224 patients. The proportion of patients who received chemotherapy varied by province, with Ontario having the highest proportion (46.4%), and Nova Scotia, the lowest proportion (38.0%). Age, stage, receptor status, comorbidities, and geographic location were associated with receipt of chemotherapy in all provinces. Ontario had the highest proportion of patients experiencing an edv (36.1%), but the lowest proportion experiencing h (6.4%). Conversely, British Columbia had the lowest proportion of patients experiencing an edv (16.0%), but the highest proportion experiencing h (26.7%). The proportion of patients having an edvh was similar across provinces (13.9%-16.8%). Geographic location was associated with edvs, edvhs, and hs in all provinces.

Conclusions

Intra- and inter-provincial differences in the use of chemotherapy and acute care were observed. Understanding variations in care can help to identify gaps and opportunities for improvement and shared learnings.

Disparities in breast cancer diagnosis for immigrant women in Ontario and BC: results from the CanIMPACT study

BACKGROUND

In Canada, clinical practice guidelines recommend breast cancer screening, but there are gaps in adherence to recommendations for screening, particularly among certain hard-to-reach populations, that may differ by province. We compared stage of diagnosis, proportion of screen-detected breast cancers, and length of diagnostic interval for immigrant women versus long-term residents of BC and Ontario.

METHODS

We conducted a retrospective cohort study using linked administrative databases in BC and Ontario. We identified all women residing in either province who were diagnosed with incident invasive breast cancer between 2007 and 2011, and determined who was foreign-born using the Immigration Refugee and Citizenship Canada database. We used descriptive statistics and bivariate analyses to describe the sample and study outcomes. We conducted multivariate analyses (modified Poisson regression and quantile regression) to control for potential confounders.

RESULTS

There were 14,198 BC women and 46,952 Ontario women included in the study population, of which 11.8 and 11.7% were foreign-born respectively. In both provinces, immigrants and long-term residents had similar primary care access. In both provinces, immigrant women were significantly less likely to have a screen-detected breast cancer (adjusted relative risk 0.88 [0.79-0.96] in BC, 0.88 [0.84-0.93] in Ontario) and had a significantly longer median diagnostic interval (2 [0.2-3.8] days in BC, 5.5 [4.4-6.6] days in Ontario) than long-term residents. Women from East Asia and the Pacific were less likely to have a screen-detected cancer and had a longer diagnostic interval, but were diagnosed at an earlier stage than long-term residents. In Ontario, women from Latin America and the Caribbean and from South Asia were less likely to have a screen-detected cancer, had a longer median diagnostic interval, and were diagnosed at a later stage than long-term residents. These findings were not explained by access to primary care.

CONCLUSIONS

There are inequalities in breast cancer diagnosis for Canadian immigrant women. We have identified particular immigrant groups (women from Latin America and the Caribbean and from South Asia) that appear to be subject to disparities in the diagnostic process that need to be addressed in order to effectively reduce gaps in care.

Utilization of bone mineral density testing among breast cancer survivors in British Columbia, Canada

Breast cancer survivors are at high osteoporosis risk. Bone mineral density testing plays a key role in osteoporosis management. We analyzed a historical utilization of bone mineral density testing in breast cancer survivors. The utilization remained low in the 1995-2008 period. Lower socio-economic status and rural residency were associated with lower utilization.

INTRODUCTION

To evaluate the utilization of bone mineral density (BMD) testing for female breast cancer survivors aged 65+ surviving ≥ 3 years in British Columbia, Canada.

METHODS

A retrospecitve population-based data linkage study. Trends in proportion of survivors with ≥ 1 BMD test for each calendar year from 1995 to 2008 were evaluated with a serial cross-sectional analysis. Associations between factors (socio-demographic and clinical) and BMD testing rates over the period 2006-2008 for 7625 survivors were evaluated with a cross-sectional analysis and estimated as adjusted prevalence ratios (PR_adj) using log-binomial models.

RESULTS

Proportions of survivors with ≥ 1 BMD test increased from 1.0% in 1995 to 10.1% in 2008. The BMD testing rate in 2006-2008 was 26.5%. Socio-economic status (SES) and urban/rural residence were associated with BMD testing rates in a dose-dependent relationship (p for trend< 0.01). Survivors with lower SES (PR_adj = 0.66-0.78) or rural residence (PR_adj = 0.70) were 20-30% less likely to have BMD tests, compared with survivors with the highest SES or urban residence. BMD testing rates were also negatively associated with older age (75+) (PR_adj = 0.47; 95% CI = 0.42, 0.52), nursing home residency (0.05; 0.01, 0.39), recent osteoporotic fractures (0.21; 0.14, 0.32), and no previous BMD tests (0.26; 0.23, 0.29).

CONCLUSION

Utilization of BMD testing was low for breast cancer survivors in BC, Canada. Lower SES and rural residence were associated with lower BMD testing rates.

IMPLICATION FOR CANCER SURVIVORS

Female breast cancer survivors, especially those with lower SES or rural residence, should be encouraged to receive BMD tests as recommended by Canadian guidelines.

Probabilistic Multiple-Bias Modeling Applied to the Canadian Data From the Interphone Study of Mobile Phone Use and Risk of Glioma, Meningioma, Acoustic Neuroma, and Parotid Gland Tumors

We undertook a re-analysis of the Canadian data from the 13-country case-control Interphone Study (2001-2004), in which researchers evaluated the associations of mobile phone use with the risks of brain, acoustic neuroma, and parotid gland tumors. In the main publication of the multinational Interphone Study, investigators concluded that biases and errors prevented a causal interpretation. We applied a probabilistic multiple-bias model to address possible biases simultaneously, using validation data from billing records and nonparticipant questionnaires as information on recall error and selective participation. In our modeling, we sought to adjust for these sources of uncertainty and to facilitate interpretation. For glioma, when comparing those in the highest quartile of use (>558 lifetime hours) to those who were not regular users, the odds ratio was 2.0 (95% confidence interval: 1.2, 3.4). After adjustment for selection and recall biases, the odds ratio was 2.2 (95% limits: 1.3, 4.1). There was little evidence of an increase in the risk of meningioma, acoustic neuroma, or parotid gland tumors in relation to mobile phone use. Adjustments for selection and recall biases did not materially affect interpretation in our results from Canadian data.

Use of physician services during the survivorship phase: a multi-province study of women diagnosed with breast cancer

INTRODUCTION

Oncologists have traditionally been responsible for providing routine follow-up care for cancer survivors; in recent years, however, primary care providers (pcps) are taking a greater role in care during the follow-up period. In the present study, we used a longitudinal multi-province retrospective cohort study to examine how primary care and specialist care intersect in the delivery of breast cancer follow-up care.

METHODS

Various databases (registry, clinical, and administrative) were linked in each of four provinces: British Columbia, Manitoba, Ontario, and Nova Scotia. Population-based cohorts of breast cancer survivors were identified in each province. Physician visits were identified using billings or claims data and were classified as visits to primary care (total, breast cancer-specific, and other), oncology (medical oncology, radiation oncology, and surgery), and other specialties. The mean numbers of visits by physician type and specialty, or by combinations thereof, were examined. The mean numbers of visits for each follow-up year were also examined by physician type.

RESULTS

The results showed that many women (>64%) in each province received care from both primary care and oncology providers during the follow-up period. The mean number of breast cancer-specific visits to primary care and visits to oncology declined with each follow-up year. Interprovincial variations were observed, with greater surgeon follow-up in Nova Scotia and greater primary care follow-up in British Columbia. Provincial differences could reflect variations in policies and recommendations, relevant initiatives, and resources or infrastructure to support pcp-led follow-up care.

CONCLUSIONS

Optimizing the role of pcps in breast cancer follow-up care might require strategies to change attitudes about pcp-led follow-up and to better support pcps in providing survivorship care.

Multigene expression profile testing in breast cancer: is there a role for family physicians?

BACKGROUND

Family physicians (fps) play a role in aspects of personalized medicine in cancer, including assessment of increased risk because of family history. Little is known about the potential role of fps in supporting cancer patients who undergo tumour gene expression profile (gep) testing.

METHODS

We conducted a mixed-methods study with qualitative and quantitative components. Qualitative data from focus groups and interviews with fps and cancer specialists about the role of fps in breast cancer gep testing were obtained during studies conducted within the pan-Canadian canimpact research program. We determined the number of visits by breast cancer patients to a fp between the first medical oncology visit and the start of chemotherapy, a period when patients might be considering results of gep testing.

RESULTS

The fps and cancer specialists felt that ordering gep tests and explaining the results was the role of the oncologist. A new fp role was identified relating to the fp-patient relationship: supporting patients in making adjuvant therapy decisions informed by gep tests by considering the patient's comorbid conditions, social situation, and preferences. Lack of fp knowledge and resources, and challenges in fp-oncologist communication were seen as significant barriers to that role. Between 28% and 38% of patients visited a fp between the first oncology visit and the start of chemotherapy.

CONCLUSIONS

Our findings suggest an emerging role for fps in supporting patients who are making adjuvant treatment decisions after receiving the results of gep testing. For success in this new role, education and point-of-care tools, together with more effective communication strategies between fps and oncologists, are needed.

Accrual of adolescents and young adults with cancer to clinical trials

Cancer is the most common disease-related cause of death in 15- to 29-year-olds in Canada [...]

Siglec-F antibody administration to mice selectively reduces blood and tissue eosinophils

BACKGROUND

Sialic acid-binding immunoglobulin-like lectins (Siglecs) are a family of receptors that bind sialic acid and mostly contain immunoreceptor tyrosine-based inhibitory motifs, suggesting that these molecules possess inhibitory functions. We have recently identified Siglec-8 as an eosinophil-prominent Siglec, and cross-linking of Siglec-8 on human eosinophils induces apoptosis. In this article, we address the in vivo consequences of Siglec engagement. We and others have identified mouse Siglec-F as the closest functional paralog of human Siglec-8, based on shared ligand-binding and expression pattern. We therefore hypothesized that Siglec-F engagement would affect levels and viability of eosinophils in vivo.

METHODS

Wild type and hypereosinophilic mice were administered Siglec-F antibody and levels of eosinophils in peripheral blood and tissue were measured. Eosinophil apoptosis (in vivo and in vitro) was determined by binding of Annexin-V.

RESULTS

Studies in IL-5 transgenic mice, displaying hypereosinophilia, show that administration of a single dose of Siglec-F antibody results in rapid reductions in quantum of eosinophils in the blood. This decrease was accompanied by reductions in tissue eosinophils. Quantum of eosinophils in blood was decreased using two separate antibodies, as well as in other mouse models (wild type mice and in a mouse model of chronic eosinophilic leukemia). Mechanistic studies demonstrated that Siglec-F antibody administration induced apoptosis of eosinophils in vivo and in vitro.

CONCLUSION

These data demonstrate that activation of innate immune receptors, like Siglec-F, can significantly reduce mouse eosinophil viability. As such, targeting Siglec-8/F may be a therapeutic approach for eosinophilic disorders.

Research, policy and practice related to survivors of childhood, adolescent and young adult cancers in British Columbia (BC), Canada: A population-based approach

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Background and Purpose: Prevalence of long term survivors of pediatric, adolescent and young adult cancers is increasing. In BC we are using a multidimensional population approach to address research and care for these survivors. Information on trends in prevalence of survivors and use of physician services are presented. Methods: We have identified a cohort of patients under 25, diagnosed from population registries since 1970, and linked their records with person-based longitudinal records of health utilization. Results: Prevalence rate of cancer survivors aged 0–59 years, originally diagnosed under age 25, increased 5 fold between 1975 and 2005, from 26 per 100,000 to 147 per 100,000; 78% were aged 20 or older. A total subgroup of 3,787 individuals surviving five years or more, diagnosed between 1970 and 1995, were identified; 2,590 (68%) of these were linked to physician visit records (excluding visits within BC's Children's Hospital) from 1986 to 2000. In year 2000, 77% of survivors had at least one physician visit; 75% of survivors saw a family physician (FP), and 44% of survivors visited a specialist physician with a specialty that could be related to a late effect. Between 1986 and 2000 survivor prevalence increased 3.3% per year; total visits by survivors to FPs increased by 11.6% per year and by 10.6% per year to specialists. In 1986, 66% of physician visits were for patients older than 20 which increased to 79% by 2000. A provincial pediatric oncology network consisting of oncologists and community care representatives has been established to implement changes to long-term follow up policy. Conclusion: The prevalence rate and utilization of health services among survivors of childhood, adolescent and young adult cancers continues to escalate. Research results, along with other published literature, will inform the development of policy and practice within the BC Network.

No significant financial relationships to disclose.

Second primary cancers among 109 000 cases of non-Hodgkin's lymphoma

An analysis of other primary cancers in individuals with non-Hodgkin's lymphoma (NHL) can help to elucidate this cancer aetiology. In all, 109 451 first primary NHL were included in a pooled analysis of 13 cancer registries. The observed numbers of second cancers were compared to the expected numbers derived from the age-, sex-, calendar period- and registry-specific incidence rates. We also calculated the standardised incidence ratios for NHL as a second primary after other cancers. There was a 47% (95% confidence interval 43–51%) overall increase in the risk of a primary cancer after NHL. A strongly significant (P<0.001) increase was observed for cancers of the lip, tongue, oropharynx^*, stomach, small intestine, colon^*, liver, nasal cavity^*, lung, soft tissues^*, skin melanoma^*, nonmelanoma skin^*, bladder^*, kidney^*, thyroid^*, Hodgkin's lymphoma^*, lymphoid leukaemia^* and myeloid leukaemia. Non-Hodgkin's lymphoma as a second primary was increased after cancers marked with an asterisk. Patterns of risk indicate a treatment effect for lung, bladder, stomach, Hodgkin's lymphoma and myeloid leukaemia. Common risk factors may be involved for cancers of the lung, bladder, nasal cavity and for soft tissues, such as pesticides. Bidirectional effects for several cancer sites of potential viral origin argue strongly for a role for immune suppression in NHL.

The determinants of Canadian children's personal exposures to magnetic fields

Study of the health effects of magnetic fields often depends on identifying determinants and hence indicators of personal exposure. This study identified determinants of children's exposure to magnetic fields and constructed a prediction model for them. For 632 children participating in a case-control study of childhood leukemia, we made direct measures of exposure over 48 h using a portable device, together with observations on candidate determinants. A child's age and sex, the proportion of time spent in the home, and their parents' education or income were very weak predictors of (logged) mean 48 h magnetic field (R(2) < 1%). More important were province (R(2) = 8.0%) and type of residence (R(2) = 11.3%). Low temperatures at the time of measurement were associated with high fields (about 20% increase for each 10 degrees C below 14, R(2) = 4.9%). Several visible attributes of wiring around residences predicted exposure, mostly captured in the Wertheimer-Leeper wire code (R(2) = 13.5%). Stationary 24 h measurement in the bedroom (R(2) = 63.3%) and spot measurements outside the house (R(2) = 40.7%) predicted personal exposures best. Adding other minor predictors increased only slightly variance explained by 24 h stationary (R(2) = 66.2%) and spot (R(2) = 46.8%) measurements. Without spot or stationary measurements, the best model was much less powerful (R(2) = 29.0%). We conclude that spot measurements outside the residence provide a moderately effective basis for estimating exposure for children living there, but do not perform as well as 24 h stationary measurements in the child's bedroom. Although several other easily-observed variables were associated with personal exposure, they were weak determinants, either individually or in combination.

Recent advances in research on radiofrequency fields and health

Since the Royal Society of Canada report on potential health risks of radiofrequency (RF) fields from wireless telecommunications in the spring of 1999, there have been several newly published reports on risks associated with the use of mobile phones. This article provides a summary of scientific research on the potential health effects of radiofrequency fields that has been reported since the original Royal Society report was published. This update also discusses several earlier results not included in the original report.

Exposures of children in Canada to 60-Hz magnetic and electric fields

OBJECTIVES

This study sought to characterize personal exposures of Canadian children to 60-Hz magnetic and electric fields and explain the variability.

METHODS

Altogether 382 Canadian children up to 15 years of age wore meters recording 60-Hz electric and magnetic fields over 2 days. Meter location was noted. Thereafter, meters measured fields in the center of the children's bedrooms for 24 hours. Personal exposures were calculated for home, school or day care, outside the home, bedroom at night, and all categories combined (total).

RESULTS

The arithmetic mean (AM) was 0.121 microT [geometric mean (GM): 0.085 microT), range 0.01-0.8 microT] for total magnetic fields. Fifteen percent of the total exposures exceeded 0.2 microT. The AM of the total electric fields was 14.4 (GM 12.3, range 0.82-64.7) V/m. By location category, the highest and lowest magnetic fields occurred at home during the day (0.142 microT) and during the night (0.112 microT), respectively. Measurements during sleep provided the highest correlation with total magnetic field exposure. Province of measurement explained 14.7% of the variation in the logarithms of total magnetic fields, and season accounted for an additional 1.5%.

CONCLUSIONS

This study has identified differences in children's magnetic field exposures between provinces. Measurements at night provided the best surrogate for predicting total magnetic field exposure, followed by at-home exposure and 24-hour bedroom measurements. Electrical heating and air conditioning, wiring type, and type of housing appear to be promising indicators of magnetic field levels.

Power-frequency electric and magnetic fields and risk of childhood leukemia in Canada

In a case-control study of childhood leukemia in relation to exposure to power-frequency electric and magnetic fields (EMF), 399 children resident in five Canadian provinces who were diagnosed at ages 0-14 years between 1990 and 1994 (June 1995 in British Columbia and Quebec) were enrolled, along with 399 controls. Exposure assessment included 48-hour personal EMF measurement, wire coding and magnetic field measurements for subjects' residences from conception to diagnosis/reference date, and a 24-hour magnetic field bedroom measurement. Personal magnetic fields were not related to risk of leukemia (adjusted odds ratio (OR) = 0.95, p for trend = 0.73) or acute lymphatic leukemia (OR = 0.93, p for trend = 0.64). There were no clear associations with predicted magnetic field exposure 2 years before the diagnosis/reference date or over the subject's lifetime or with personal electric field exposure. A statistically nonsignificant elevated risk of acute lymphatic leukemia was observed with very high wiring configurations among residences of subjects 2 years before the diagnosis/reference date (OR = 1.72 compared with underground wiring, 95% confidence interval 0.54-5.45). These results provide little support for a relation between power-frequency EMF exposure and risk of childhood leukemia.

Childhood cancer and environmental contaminants

This article reviews the available epidemiologic evidence for relationships between the development of cancer in childhood and environmental agents, specifically chemicals, ionizing radiation, low-frequency electromagnetic fields, and infectious agents. Chemical exposures include medications and other drugs, components of diet, and second-hand exposure to industrial chemicals and to environmental carcinogens. Ionizing radiation is the only well-established risk factor for childhood cancers. Suggestive associations with excess childhood cancer risk have been found with exposures to paints, petroleum products, solvents, pesticides and metals. An excess risk of brain tumours has been reported with ingestion of n-nitroso compounds, and there have been positive findings relating leukemia risk and infections. Studies of risk of childhood cancer with parental use of alcohol and with parental smoking have been generally negative, while the inconsistencies and generally low risks reported in studies of power-frequency electromagnetic fields do not support a causal relationship.

The development of mothers' understanding of infant crying

This study examines the development of mothers' understanding of their infants' crying. Semistructured tape-recorded interviews were conducted with 17 mothers at 6 weeks, 10 weeks, and 16 weeks postpartum. The mothers (9 primiparous, 8 multiparous) were chosen for their good health status and for their immediate support system. Two major themes were identified from the interviews. In general, it was found that as the mothers became more experienced, the understanding of the cry situation became more complete and soothing was more effective. The relation between crying and soothing became more differentiated, more cohesive, and more complete. The effect of experience on understanding was particularly dramatic in the case of multiparous mothers. Both health promotional and illness prevention programming are proposed as nursing care measures for mothers of crying infants. The important assumptions underlying each approach are delineated.

Calculating the prevalence of cancer

Incidence, prevalence and mortality are commonly used measures to assess the impact of disease on human populations. Prevalence, although regularly assessed for a number of different diseases, has only had recent use to measure the impact of cancer. The calculation of the prevalence of cancer presents several difficulties since there is no reporting mechanism established to measure the proportion of the community that has the disease. In the absence of such a mechanism, mortality data linked to incidence data from cancer registries have been used. The assumption is made that once diagnosed with cancer an individual remains a prevalent case until death. In this paper we present alternatives to this assumption and use them to produce estimates of cancer prevalence. We illustrate the effect of these assumptions on the calculated prevalence of cancer using data from the British Columbia Cancer Registry.

Maternal and gestational factors in cryptorchidism

Previous epidemiological studies of cryptorchidism have led to the hypothesis that the risk of undescended testis is associated with excess oestrogen exposure during pregnancy. A case-control study was undertaken to test this hypothesis, comparing mothers of affected boys (244) and normal male births (488) born within six months of a case selected randomly from the British Columbia population. Information was collected on the mother's reproductive history, family history, and past medical history, and events surrounding all pregnancies ending in a birth. The results were analysed using both the population-based sample of male births and the male sibs of cases as control groups. Neither exogenous oestrogen exposure, nor any of the pregnancy-related variables hypothesized to be indirect indicators of endogenous oestrogen exposure, including bleeding and nausea and/or vomiting, were found to be significantly associated with risk of undescended testes in either comparison. More mothers with later index births reported menstrual irregularity greater than half the time, and smoking, thought to have a protective effect, was more prevalent among case mothers than control mothers. No other variables were significantly different between case and control mothers. The results of this study do not support the hypothesis that elevated exogenous or endogenous oestrogen exposure during pregnancy increases the risk of undescended testis in male children.

Changing epidemiology of cancer

At current rates, approximately one in three Canadians will develop cancer, and one in four will die from it. For each sex, three cancer sites account for more than 50% of all new diagnoses and cancer deaths, these being lung, prostate, and colorectum in men and breast, colorectum, and lung in women. Although the total numbers of new cases and cancer deaths have risen, the overall cancer incidence and mortality rates have increased only slightly. The ranking of specific sites have changed, however; most notably, lung cancer has moved from the fifth to the second most common site of cancer death in women since 1970. The authors review trends in cancer incidence and mortality in Canada. Changes in lifestyle and behaviour could reduce cancer incidence and mortality.

Growth parameters in normal fetuses

A total of 14 linear measurements, seven ratios of linear measurements, and the weights of eight organs were taken from 100 normal fetuses. The fetuses had been therapeutically aborted between 11 and 19 weeks of gestational age by prostaglandin induction or hysterotomy. Measurements were obtained from at least five fetuses for each week of development age. A correlation matrix was calculated in order to identify those variables that showed a significant relationship with each other and with total body measurements. Significant correlations were obtained between crown-rump length and the following: head circumference, femur length, and humerus length. These three measurements were also significantly correlated with body weight. First-order regression equations were produced for these significantly correlated variables. This information can be used to estimate fetal growth even when the fetus is incomplete.

Contrasting effects of maternal fertility and birth rank on the occurrence of neural tube defects

The relationships between the occurrence of anencephalus and spina bifida, sibship size and birth rank were examined, using linked records for births in British Columbia. Comparison of 414 sibships in which at least one infant had a neural tube defect with 1362 randomly chosen unaffected sibships showed that the affected sibships were larger. There were both more births than expected after the affected birth, and shorter intervals between births before the affected birth. Within sibships, the risk of anencephalus or spina bifida decreased strongly with increasing birth rank. No associations were seen with maternal age at first birth.